Tire pressure indicator



p 1949. s. ROBERTSON 2,481,534

TIRE PRESSURE INDICATOR Filed May 26, 1947 3 Sheets-Sheet l Fig. I.

I )1 winter Stewart Robertson flaw I S. ROBERTSON TIRE PRESSURE INDICATOR Filed May 26; 1947 3 Sheets-Sheet 2 wink A its 7% 63/5 septa 13 1949. s. ROBERTSON 2,481,534

' TIRE PRESSURE INDICATOR Filed May 26, 1947 3 Shee'ts-Shet s Inventor Sfe wan Fwberfson gllAlhk-ZF By 36 Patented Sept. 13, 1949 TIRE PRESSURE INDICATOR Stewart Robertson, Oakland, Calif., assignor of thirty-three and one-third per cent to David Robertson, Oakland, Ill.

Application May 26, 1947, Serial No. 750,394

2 Claims.

This invention relates to tire inflation indicators, and the primary object of the invention is to provide a practical device for indicating to the driver of a motor vehicle, while the vehicle is being driven, whether the pressure in each of the pneumatic tires of the vehicle is normal, more or less above or more or less below normal.

Another object is to provide a comparatively simple device of the above kind which may be readily installed on motor vehicles of difierent makes.

A further object is to provide a device of the above kind including pressure-responsive circuitcontrolling means which embodies an annular elastic diaphragmrotatable with and concentric with the axis of each vehicle wheel and connected to the tire of said wheel, a switch including a casing mounted on a stationary part of the vehicle inwardly of the wheel and carrying a series of fixed contacts, and a movable contact co-acting with said fixed contacts and movable transversely of the vehicle, and novel means for moving said movable contact in response to expansion and contraction of said diaphragm.

Other objects and features of the invention will become apparent from the following description when considered in connection with the accompanying drawings, in which:

Figure 1 is a fragmentary vertical transverse section through a wheel having a pneumatic tire and equipped with pressure-responsive circuitcontrolling means constructed in accordance with the present invention;

Figure 2 is a central longitudinal sectional view of the fitting for coupling the air tube of the diaphragm with the inflation valve of the inner tube forming part of the pneumatic tire;

Figure 3 is a transverse section taken on line 3-3 of Figure 2;

Figure 4 is a fragmentary vertical section taken on line 44 of Figure 1;

Figure 5 is a vertical section taken on line 5-5 of Figure 1;

Figure 6 is a vertical section taken on line 6-6 of Figure 5;

Figure 7 is a fragmentary perspective view showing the instrument board of the vehicle equipped with indicator lights in accordance with the present invention;

FigureB is an enlarged fragmentary vertical section taken on line 8-8 of Figure 7; and

Figure 9 is a circuit diagram showing the electrical connections between the various elements of the device.

Referring in detail to the drawings, 5 indicates a conventional vehicle wheel carrying a pneumatic tire composed of a shoe 6 and an inner tube 1. The wheel also has the usual brake drum 8 secured thereto and rotatable therewith, which brake drum is closed at its inner side by the usual closure disc 9 fixed on a stationary part of the vehicle, such as the housing ID of the rear axle H on which the wheel 5 is mounted.

In accordance with the present invention, pressure-responsive circuit-controlling means is 'associated with the wheel 5 and includes an annular channel member l2 concentrically mounted within and secured to the drum 8 so as to rotate with the latter. The channel member I2 is open at its inner side, and an annular elastic diaphragm I3 is disposed within and rotatable with said channel member. The diaphragm I3 is connected with the inner tube 1 by means of an air tub'e I 4 and a fitting l5 coupling one end of the air tube M with the inflation valve l6 of inner tube I. Annular presser plates l1 and I8 are slidable in the channel member I2 transversely of the wheel 5, yieldable means, such as leaf springs l9 being provided to move the pressure plates outwardly upon contraction of the diaphragm [3 due to reduction of air pressure within the latter. The presser plate I! is disposed at the inner side of diaphragm l3 and is keyed at 20 to the channel member l2. The other presser plate [8 is disposed inwardly of the presser plate I! and is connected to the closure disc 9 so as to be held against rotation thereby. For the latter purpose, the presser plate 18 is provided with inwardly projecting tubular members 2| which are slidably received on outwardly projecting lateral members 22 fixed to the closure disc 9. The springs 19 are preferably centrally riveted to the presser plate I8 and have their ends bearing against closure disc 9. Anti-friction bearing means 23 is provided between the presser plates l1 and 18 so as to freely permit rotation of the presser plate ll relative to the presser plate l8.

The circuit controlling means further includes a switch embodying a casing 24 and mounted on the stationary part l0 and having therein a lonitudinal series of fixed contacts 25 and a second longitudinal series of fixed contracts 26. Each contact 25 is opposed to a contact 26. Movable longitudinally of the casing 24 is a movable contact 21 adapted to bridge one pair of contacts 25 and 26 at a time. This movable bridging contact 2'! is carried by a rod 28 slidable through one end of casing 21 and suitably attached to one of the tubular members 2| carried by the presser plate l8. The arrangement is such that when diaphragm. I3 is expanded, the contact 21 is moved in one direction, and when diaphragm l3 con-v tracts, said contact 21 is moved in the opposite direction. There are five pairs of contacts 25 and 26 in the casing 24, and the movable contact 21 should bridge the central pair of contacts 25 and. 26 when diaphragm I3 is expanded by normal air pressure from tube 1. In order to effect this relationship, the casing 24 is adjustable transversely of the vehicle toward or away from the Wheel 5. For this purpose, a guide 29 is fixed on the stationary member I0, and casing 24 has a base 30*sli'dable in said guide=29 and adjustable with respect/to the latter by means of an adjusting screw 3 I.

Each contact 25 is conected to one side of a difierent lamp 32, the other side of which is grounded at 33. Also, all of the contacts"26 are connected by a wire 34 to one contact of the usual ignition switch 35 so'that current-is only supplied to the contacts 26 from the source of current 38 when the ignition switch 35 is closed. The other side of the source 36 is grounded at. It is to be understood that there is oneipressureresponsive circuit-controlling switch, as above described, for each wheel of the vehicle, andthe contacts 26-of each such switch areconnected to the wire 34 asshown in Figure 9. Also, the contacts 25 of each such switch are connected to additionaldiiferent lamps32 as above described so that there is one set of lamps controlled by each pressure-responsive switch. All of the lamps 32 are preferably arranged within a single lamp box 38 mounted in an opening of the instrument board 39 of the vehicle. This lamp box includes a face-plate 40 having a plurality of apertures 41 which are so'arranged that one is proVidedfor each-lamp 32. Glass covers 42 are provided for apertures 2|, that for the central lamp of each set being preferably of a green color, those for the e'nd lamps of each set preferably being of a red color, and those for the lamps between the central and end lamps preferably being of an orange-color or the like as indicated by the shading in Figure '7. The lamp box 38 is preferably partitioned as indicated at 43 in Figure 8 so as to provide four compartments, with one set of lamps in each compartment. By suitably labeling the different sets of colored plates 42, the particular wheel for which each set of lights is provided will be known to the driver.

In operation, when the pressure in the tube i is normal, the diaphragm l3 will be'expanded to a condition wherein the contact 21 bridges the central contacts 25 and 26 and closes the circuit of the central lamp 32' of the associated set. This displays'a green light so as to indicate to the driver that the pressure in the associated tire is normal. Should the pressure in the tire drop slightly below normal, the contact 2'! will 'be moved so as to close the'circuit of the'la'mp 32 at one side of that which shows the green light, thereby showing an orange light at the proper ;side to show below-normal pressure. Should the pressure go considerably below'n'ormal, the proper end lamp will be lighted toshow a red light, thereby indicating that the pressure iscon- 'si'derably below normal and that the tire pressure should be increased. On the otherhand, should the pressure rise slightly above normal for any reason the orangelight at the opposite side of the green light will be lighted to indicate that "fact, whereas abnormal high pressure will be shown by the lighting of lamp 32 at the latter side 'ofthe green light which shows ared light, thereby indicatingthat the pressure is considerably above normal and should be reduced.

'As shown in'Figures 2 and 3, the fitting 15 has a swiveled nut 44 adapted to thread on thevalve stem [9 of tube 1. A triangular plug 45 is threaded at 46 into the casing of fittings l andis adapted, when screwed inwardly, toengage the stem 41 of the valve core in the valve stem [6 so as to unseat the-valve member of said stem l6 and thereby'allow the pressure within tube '1 to flow todiaphragm I3. The air tube [4 is connected to a branch nipple 48 of the fitting [5. Plug 45 has an axial bore 49, and is provided with a plurality of ports 56 'which'extendthrough the sides of plug from the bore 49. The usual inflation valve 5| is provided in the outer end of the bore 49 of plug 45, and the arrangement is such that an inflation h'os'emay be coupled to the threaded outer end 52 of.plug for inflating the tube 1 without disc'onnectin'g the'fitting l5 from the inflation valve stem l6of the-inner tube. At the same time, by rotating nut 44, fitting [5 may be readily uncoupledfrom the inflation valve stem [6 of tube 1 when it becomes necessary to remove the tire of the wheel 5 for repair.

From the foregoing description, it will be seen that I have provided a simple and highly'efiicient device for indicating the various stages of pressure in a tire, said device being adaptable for installation upon automobiles of various makes. Minor changes in details of construction are contemplated, such as fall within the scope of the invention as claimed.

What is claimed is:

1. In a tire inflation indicator for a motor vehicle having wheels equipped with pneumatic tires, and wherein a brake drum is carried by and rotatable with each wheel, and a stationary closure disc for the brake drum is carried by a stationary member of the vehicle, pressure-responsive circuit-controlling means including an annularchannel member concentrically mounted within and rotatable with the brake drum, an annular elastic diaphragm disposed within and rotatable with said channel member and connected with the tire, annular presser plates slidable in the channel member transversely of the wheel, yieldable means to move the presser plates outwardly upon contraction of said diaphragm, one of said presser plates'being disposed at the inner side of said diaphragm and keyed to the channel member, the other pressure plate being disposed inwardly of said one presser plate and slidably connected to said closure disc so as to be held against rotation'thereby and to be movable transversely of the wheel relative thereto, anti-friction bearing means between said presser plates, and a multiple signal-circuit controlling switch including a casing mounted on said stationary'member of the vehicle and carrying a series of pairs of fixed contacts and a movable contact movable for successively co-acting with said pairs of fixed contacts-and mechanically connected to said other presser plate for movement thereby.

'2. The construction defined in claim 1, in combination with means for adjusting said switch casing transversely of the vehicle toward or from said wheel for eflecting predetermined relationship between said movable contact and a certain pair of said fixed contacts when the'pressure in the-tire is normal.

STEWART ROBERTSON.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,349,139 Denmire -Mar. 15, 1932 2,071,256 Dobbs Feb. 16, 1937 2,119,287 Pratt May 31, 1938 FOREIGN PATENTS Number Country Date v 1,-331 GreatBritain Janf18,19l1 

